The present invention relates to a semiconductor photodetector, and more particularly to a silicon-based semiconductor photodetector with an improved optical fiber guide groove.
FIG. 1A is a fragmentary cross sectional elevation view illustrative of the first conventional silicon-based semiconductor photodetector provided adjacent to an optical fiber guiding trench groove formed in a semiconductor substrate taken along an IA--IA line in FIG. 1B. FIG. 1B is a plan view illustrative of the first conventional silicon-based semiconductor photodetector provided adjacent to an optical fiber guiding trench groove formed in a semiconductor substrate. This first conventional silicon-based semiconductor photodetector has an optical absorption layer with an edge portion directly shown to the optical fiber guiding trench groove. Recombination energy levels appear on the edge portion of the optical absorption layer. This causes a leakage current flowing through a p-n diode in the photodetector or a dark current of the photodetector. As a result, the signal-to-noise ratio is deteriorated.
FIG. 2A is a fragmentary cross sectional elevation view illustrative of the second conventional silicon-based semiconductor photodetector provided adjacent to an optical fiber guiding trench groove formed in a semiconductor substrate taken along an IIA--IIA line in FIG. 2B. FIG. 2B is a plan view illustrative of the second conventional silicon-based semiconductor photodetector provided adjacent to an optical fiber guiding trench groove formed in a semiconductor substrate. The light having been propagated through the optical fiber is transmitted through many interfaces of the different materials having different refractive indexes. This means that the light is partially reflected many times at the interfaces of the different materials having different refractive indexes. This results in increased optical coupling loss.
FIG. 3 is a schematic plan view illustrative of the third conventional silicon-based semiconductor photodetector provided adjacent to an optical fiber guiding trench groove formed in a semiconductor substrate. The edge portion of the optical absorption layer is positioned adjacent to the end portion of the optical fiber. This means that the end portion of the optical fiber may hit to the edge portion of the optical waveguide or the optical absorption layer. The end portion of the optical fiber 13 and the optical absorption layer 6 or the silicon oxide isolation layer 4 may receive damage due to the direct contact to the end portion of the optical fiber.
In the above circumstances, it had been required to develop a novel semiconductor photodetector formed over a substrate and being positioned adjacent to an optical fiber guiding groove also formed in said substrate bounding structure, said semiconductor photodetector having an optical waveguide layer including an optical absorption layer free from the above problems and disadvantages.